Field of the Invention
The present invention relates to a black electrode substrate provided with a metal wiring having low resistance and improving visibility thereof, a method of manufacturing a black electrode substrate and a display apparatus provided with the black electrode substrate.
The black electrode substrate is used for an in-cell type display device integrating capacitive type touch sensing functionality into the liquid crystal cell.
Discussion of the Background
Generally, display devices configured to use a touch panel are well known. The touch panel is disposed on a display surface of a display device which is provided in portable equipment such as smartphones or tablet computers. The touch panel is used as an input device which detects a contact between a finger or a pointer or the like and the touch panel. The major detection method for detecting a position of the finger or the pointer on the touch panel is a capacitive detection method which detects capacitive-change on the touch panel caused by a contact between the finger or the pointer and the touch panel.
The structure of providing the touch panel in the display device may increase the entire thickness or weight of the display device. Accordingly, the touch panel is considered as an unnecessary component in this structure of the display device. In this respect, a touch panel mainly using an organic film has been known, which reduces weight of the display device. However, even with this type of touch panel, it is difficult to avoid an increase of the entire thickness of the display device. Further, in the case where the display device is provided with the above-mentioned touch panel and high definition pixels, there is a disadvantage that necessary input (pen input) onto the touch panel is difficult to achieve.
Specifically, when the display device has high definition pixels of 400 ppi (pixel per inch), or 500 ppi or more, the pixel pitch is around 10 μm to 20 μm. Thus, if the display device has the above-mentioned touch panel and such high definition pixels, most of touch panels do not tolerate the pen pressure of the pen. Moreover, such display devices raise problems, including a problem of limited resolution in the opening configuring the input portion of the touch panel, or a problem of difficulty in achieving sufficient resolution of the touch panel to obtain high definition of the display device. Therefore, touch sensing technique for the touch panel is required to be sophisticated.
In recent years, development of so-called ‘in-cell’ touch-sensing technique (hereinafter referred to as in-cell display device) without using a touch panel has been developed, in which the touch sensing function is provided in the liquid crystal cell or in the display device.
For the above-described display device, generally, a configuration provided with a color filter substrate and an array substrate is known. The color filter substrate is composed of a plurality of regularly-arranged colored layers, and the array substrate includes active elements such as TFT (Thin Film Transistor) disposed therein.
For the in-cell display device, an in-cell structure provided with a pair of touch sensing electrode group has been developed. The pair of touch sensing electrode group is provided in either the color filter substrate or the array substrate, or provided in both of the color filter substrate and the array substrate. According to this structure, by detecting a change in electrostatic capacitance produced between touch sensing electrode groups, a touch sensing functionality can be achieved to detect an input-position of a finger or a pointer or the like.
In the case where an organic film is used as a base material of a touch panel, expansion and contraction of the base material (e.g., thermal expansion coefficient) is large. Hence, it is difficult to align positions (i.e., alignment) between a red pixel pattern, a green pixel pattern and a blue pixel pattern and a black matrix pattern, which compose fine pixels each having a size of approximately 10 μm to 20 μm. Therefore, the organic film base material is difficult to use for high-definition color filter substrates. As a conventional type display device, for example, display devices disclosed in PTLs 1 to 3 are known.
PTL 1: JP-A-2011-065393
PTL 2: JP-A-2013-540331
PTL 3: WO 2011-052392